The herbicidal active compound clomazone is known from U.S. Pat. No. 4,405,357 and is generally used to control weeds in various crops. The herbicidal active compound pethoxamid is known from European patent application no. EP 206251-A1 and is generally used to control weeds in various crops such as control of grass weeds and broad-leaved weeds.
Clomazone is known to be a very volatile organic compound to an extend so that clomazone applied in a target area may move to adjacent areas and there cause discoloration, most typically whitening or some degree of bleaching, of a variety of crops, trees, or decorative plants. While this bleaching may be temporary when plants are exposed to sufficiently low concentrations, it is undesirable even when not causing the destruction of the affected plant. Accordingly appropriate use instructions for clomazone is often found on product labels of commercially available clomazone products and in particular on emulsifiable concentrates formulations comprising clomazone in order to prevent exposure to clomazone sensitive plants. Methods of reducing the volatility of clomazone, i.e. to prevent or reduce vapor transfer of clomazone to plants which are not target of application, are proposed in U.S. Pat. Nos. 5,597,780 and 5,583,090 in which encapsulation techniques are applied as to prepare microcapsule suspension formulations of clomazone.
In crop protection products, it is always desirable to increase the specific activity of an active ingredient and the reliability of action. It is an object of the present invention to provide mixtures which comprise a compound A which is clomazone, and the compound B which is pethoxamid which are selective in crops to control undesirable harmful plants. Surprisingly, it has now been found that combinations of these active compounds exhibits a synergistic effect when used for the control of harmful plants. Further it has been found that by combining clomazone with pethoxamid the volatile nature of clomazone is significantly reduced.